Molding sand



United States Patent 3,210,203 MOLDING SAND Jack C. Cowan, Hugh G. Gainey, and Harvey M. Oyler IH, Houston, Tex., assignors to National Lead Company, New York, N.Y., a corporation of New Jersey No Drawing. Filed Dec. 20, 1962, Ser. No. 245,975

8 Claims. (Cl. 106-3835) This application is a continuation in part of Serial No. 213,094, filed July 30, 1962.

This invention relates to molding sands such as are used for the casting of metals, and more particularly to an improvement in molding sands of the type which are bonded with materials other than ordinary clay as such and liquids other than water.

As is well known, in the sand casting of metals a molten metal is poured into a mold formed from a suitable comminuted temperature-resistant mineral, commonly known as sand, and indeed generally consisting of quartz sand, which is bonded by .the use of a relatively minor amount of suitable bonding agent, which most commonly has been clay tempered with some water.

In recent years, it has been realized that sand clay systems of this relatively simple type are not ideally suited to all types of casting, and especially as metal founding technology becomes more and more complex, quite different systems have been developed for sand molds.

An important recent development consists in the utilization of an organophilic clay, using a material such as a petroleum oil to produce the bond. Non-aqueous systems of this type are described, for example, in Canadian Patent 572,142 and U.S. Patent 3,027,265. Even such systems fall short of perfection, however, and the present invention is concerned with improvements in essentially non-aqueous molding sand compositions of this general type.

An object of the present invention is to provide a molding sand containing a completely organic bonding agent which exhibits improved effectiveness in a novel nonaqueous vehicle.

Another object of the invention is to provide a molding sand containing such an organic bonding agent together with an organophilic clay of improved effectiveness by reason of a novel non-aqueous liquid.

Another object of the invention is to provide a molding sand bonded with an organic bonding agent and including a liquid phosphate ester.

Other objects of the invention will become apparent as the description thereof proceeds.

Generally speaking, and in accordance with an illus trative embodiment of our invention, we combine, so as to form a molding sand mix; a foundry sand; and a binder which consists of a mixture of an organic liquid as hereinafter described in greater detail, but which contains a liquid phosphate ester of a type hereinafter specified, together with a long chain alkyl ammonium humate and which may be conjoined with an organophilic clay in any proportion from zero to four parts of the organophilic clay for each part of the long chain alkyl ammonium humate. While not at all necessary for the practice of the invention, other additives common in the non-aqueous molding sand art may also be present, such as for example silica flour, finely divided iron oxide, and the like.

3,210,203 Patented Oct. 5, 1965 ice Those skilled in the art are Well acquainted with foundry sands generally, and consequently these need not be described in any great detail herein save to state that those molding sands commonly used in the conventional clay-bonded sand molds are likewise well-suited for use in our invention. These are generally quartz sand, the

particle size of which may be varied over a wide range, a

which by way of illustration and not limitation may be, for example, from about 40 to about grain fineness number (GFN) as determined by the standard methods of the American Foundrymens Society. Olivine sand is often used because of its freedom from silicosis hazard; and zircon sand may be used especially for very high temperature casting.

The alkyl ammonium humate is fundamentally an onium salt of humic acid. The humic acid is most readily and economically obtained from lignite, the alkali-soluble portion of which may be considered to be humic acid for the purpose of this invention, and indeed that is the case from a chemical standpoint.

Humic acid is a material of wide distribution, being present in soils, peat and coals, especially coals of the .type known as lignite or brown coal. Although the exact details of its chemical structure are not completely known, it is a surprisingly uniform substance considering the variety of source materials of which it represents a natural product of degradation, such as leaves, wood, and the like vegetable organic matter. It is an acid, in which carboxyl and phenolic hydroxyl groups contribute basecombining ability. It is soluble in alkalies, such as caustic soda and sodium carbonate, has a deep brown color, and is readily soluble in water when converted t its alkali metal salt, which may be then termed an alkali metal humate, the commonest example of which is sodium humate.

As indicated, humic acid is present in soils and peat, and may readily be extracted from these by known means, most commonly by treatment with dilute aqueous alkali. Whenever it is a matter of producing a commercial humate, that is, whenever economic considerations are of importance, then the humic acid is nearly always derived from its richest common source, which is lignite, of which there are vast deposits distributed throughout the world, including the United States, and particularly the states of North Dakota, Texas, New Mexico, and California.

The alkyl ammonium humate used in the practice of our invention may be more particularly described as a salt of humic acid, viz., a humate, in which the cation is a substituted ammonium ion, in which one or more of the hydrogen atoms originally present in the ammonium ion is substituted by an alkyl radical, and in which at least one of the said alkyl radicals has from 14 to 22 carbon atoms in a straight chain. It will be clear from this summation that the valence positions of the nitrogen atom which are not occupied by hydro-gen atoms may be either long alkyl chains, of the type just described, or may be short alkyl chains, from C t C that is, methyl through tridecyl, or phenyl or benzyl radicals, as long as at least one alkyl radical is present in the range of at least C to C which in the methane series corresponds to tetradecyl through docosyl.

By way of further explanation of the nature and types of the alkyl ammonium humate compounds which we a a use in our invention, we give the following table showing typical members of the series:

TABLE I Stearylammonium humate Oleylammonium humate Palmitylammonium humate Docosylammonium humate Methylstearylammonium humate Laurylstearylammonium humate Butyldocosylammonium humate Diphenylstearyl ammonium humate Benzyldiethyldocosylammonium humate Phenyldibutyloctadecylammonium humate Dirnethyldi-(hydrogenated tallow fatty alkyl) ammonium humate Methyltri-(hydrogenated tallow fatty alkyl) ammonium humate l-hydroxyethyl, Z-heptadecenyl, Z-imidazolinium humate l-benzyl, l-hydroxyethyl, Z-heptadecyl, Z-imidazolinium humate We use the term alkyl ammonium in the broad sense, wherein ammonium indicates an onium cation in which the basic atom is pentavalent nitrogen. Thus the term includes substituted ammonium cations in which two or more of the substituted positions may form part of a ring, as is the case in the imidazolinium compounds listed above. It will be further understood that the above listing is illustrative and by no means exhaustive.

Generally speaking, the alkyl ammonium humate compounds to be used in our invention may be produced by bringing together humic acid and the alkyl ammonium compound in its base form. The base and the acid neutralize each other with salt formation, so as to produce an alkyl ammonium humate in accordance with the invention. Another general method of preparation is to convert the humic acid to a simple salt by reaction with an alkali, so as to produce sodium humate, potassium humate, ammonium humate, and the like, by reaction with sodium hydroxide, potassium hydroxide, or ammonium hydroxide, respectively. The alkyl ammonium compound is caused to be present in the form of a simple salt. Thus, a primary, secondary, or tertiary amine may be reacted with a simple acid such as hydrochloric, acetic, and the like to give the corresponding substituted ammonium chloride or acetate, respectively. This method of procedure has the advantage that the simple substituted ammonium salts, and the simple humates as described, are both water soluble, so that solutions of each reactant may be made, and the reaction completed by mixing the solutions together. To give a simple example, octadecyl amine is treated with an equivalent quantity of acetic acid to give octadecylammonium acetate. This is then dissolved in several times its weight of water. Separately, humic acid is converted to sodium humate by treating lignite, for example, with sodium hydroxide to neutrality followed by filtering off the insoluble portion of the lignite. The solution of sodium humate thus formed is mixed with the solution of octadecylammonium acetate in stoichiometrically equivalent proportions, whereupon there occurs a quantitative precipitation of octadecylammonium humate. The equivalent weight of the humic acid can readily be determined in any known fashion applicable to acids generally, such as, for example, by titration of sodium hydroxide using an electrometric pH meter.

A somewhat special case is presented by the quaternary substituted ammonium salts, which have no free base form. A simple example is trimethyl octadecylammonium chloride. In its quaternary salt form, it is already available for reaction with an alkali humate such as sodium humate, and it may also be reacted directly with humic acid, although the reaction is accelerated by adding some base such as sodium hydroxide to the reaction mixture to neutralize the acid which is formed as a result of the reaction, which in the particular example considered here would be hydrochloric acid. The quaternary ammonium compounds may be in their hydroxide form, of course, and may then be reacted directly with humic acid.

The organophilic clay is chosen from the group which consists of organophilic montrnorillonite and organophilic attapulgite and indeed mixtures thereof in any proportion. Such organophilic clays are now a well known article of commerce, and are described in extensive technical and patent literature. In general, organophilic clays are made by starting with a clay of substantial base ex change capacity, the most commonly'used of which are montmorillonite as represened, for example, by Wyoming bentonite or by hectorite, and attapulgite, and effecting a cation exchange by replacing the bases present in the clay, which may be for example, sodium, calcium, hydrogen and the like, with a long chain onium cation, which indeed is most often a long chain alkyl ammonium ion, and may be chosen from the same class already described hereinabove in connection with the alkyl ammonium humate. Organophilic clays are described in Hauser Patent 2,531,427; Jordan Patent 2,531,440; Miericke Patent 3,027,265; and Canadian Patent 572,142; and indeed many others. They are also described in the book Clay Mineralogy by Ralph E. Grim, New York, 1953, pages 265269; and in the book entitled The Colloid Chemistry of Silica and silicates by Ralph K. Iler, Ithaca, 1955, pages 225-226. Organophilic clays are commercially available under the trademark Bentone. In general, the organophilic clays commercially available and useful in our invention have within narrow limits the exact amount of long chain onium ion reacted with the clay which corresponds to the cation exchange capacity of the latter. Organophilic clays are generally produced and are commercially available in the form of a fine, dry powder, generally about 200 mesh.

The organic liquid which is used together with the alkyl ammonium humate and, when present, with the organophilic clay in order to form a binder or bonding agent for the sand so as to make it into a moldable composition consisting primarily of from 25% to by weight of a liquid phosphate ester of a type to be described hereinbelow, the balance (of 75% to 0%) being selected from a very large group of secondary organic liquids. We have investigated a large number of such organic liquids, and have found that those which are suitable to be combined with the liquid phosphate ester are characterized by having a molecular weight of at least 125. Suitable organic liquids, which incidentally meet the criterion of molecular weight just stated, are normal octyl alcohol; tall oil; nonyl phenol; polyethoxylated nonyl phenol; various aromatic and paraffinic oils such as diesel oil, fuel oil, coal tar oil, and the like; the polyethylene glycols commercially available, for example, under the trademark Carbowax and having average molecular Weights from about 200 to about 400; the analogous polypropylene glycols which again have molecular weights from about to about 1,000; and the like. Mixtures of these various liquids are also quite useful. Examples of the latter are mixtures in various proportions of diesel oil and octyl alcohol.

The liquid phosphate ester which forms an essential component of the novel compositions of our invention is a phosphate ester of an ethoxylated alkyl compound (which may be, for example, an alkyl phenol) corresponding to the following formula:

R R POOH where R can be R or OH and R is:

R -O-(CH CH O),,

where n varies from 2 to 18 and where R is chosen from the group consisting of straight chain alkyl radicals from C to C ortho R -phenyl radicals and ortho-para di R -phenyl radicals, said R being C to C alkyl. Esters of this type are commercially available. In these esters, when R is R -phenyl, the alkyl groups on the benzene ring are most conveniently made by the polymerization of low molecular weight olefins. When the alkyl, i.e., R is nonyl, this may be derived from tripropylene and indeed we find that best.

The manner in which these liquid phosphate esters may be made is Well known to those skilled in the art, and indeed has been described in great detail in US. Patent No. 3,004,056, the disclosure of which is incorporated herein by reference. As will be seen by consulting Patent No. 3,004,056, these esters are made by phosphating poly (ethylene oxide) derivatives of long chain alcohols or of phenolic compounds containing one or more alkyl substituents in the phenol ring. Phenol derivatives of the latter type are described in US. Patents No. 2,213,477 and 2,593,112, the disclosures of which are incorporated herein by reference.

We have found particularly effective those liquid phosphate esters corresponding to the above chemical specification, in which the R is dinonyl phenyl, and in which the ethylene oxide to alkyl phenyl ratio is respectively and 15. That is, n in the above formula is 10 and for the two especially desirable compounds which we use. It will thus be seen that these two compounds are very close to Example 7 of the tabulation which appears in column 6 of U.S. Patent No. 3,004,056, and indeed differ therefrom only in that n is 10 and 15, respectively, instead of 7. These are mixed monoand di-esters, that is, approximately one-half of the R is R in the terms of the structural formulation given hereinabove. For convenience, these two preferred compounds will occasionally hereinafter be referred to as Liquid Phosphate Ester A and Liquid Phosphate Ester B, respectively.

Another highly effective liquid phosphate ester, which for brevity We will designate Liquid Phosphate Ester C, is that in which in terms of the above formulation, n is 2, R is the alkyl radical from hydrogenated tallow fatty acid, which of course is a mixed alkyl having approximately C12, C14, C16 and C13, R2 being mixed R and OH, roughly equimolar. It will be seen that Liquid Phosphate Ester C is thus very close to the product of Example 11 of US. Patent No. 3,004,056.

A recent description of these liquid phosphate esters corresponding to the general formulation already given appears in the Journal, Chemical and Engineering News, December 25, 1961, pages 40 and 41.

The especially preferred liquid phosphate esters just referred to are highly viscous liquids or very soft semiliquid pastes, wtih ASTM pour points in the range 30" F. to 140 F., wtih a density very close to that of water, and a pH in 10% aqueous solution of between 1.8 and 2.2. They are freely soluble in aromatic solvents such as toluene, for example. As will be clear from the structural formula given hereinabove, at least one acid-forming hydrogen is present in the phosphate radical, which accounts for the acidic pH.

We find that the utilization of the liquid phosphate esters in the compositions disclosed and claimed herein leads to a number of surprising advantages. Most readily apparent in making up compositions with and without the liquid phosphate esters is the increase in the green compression strength of the molding sand composition. This will be illustrated by examples hereinbelow.

Other advantages which are especially apparent in the actual utilization of the molding sand compositions in metal casting operations arise from the fact that if the liquid phosphate ester is omitted and its place taken by mineral oil, for example, which indeed was the common course of procedure prior to our instant invention, then with most metals and most conditions of casting, some reduction of the oil to carbon by the molten metal takes place which under favorable conditions gives a smooth finish to the casting, but which quite frequently takes place to such an extent that a wrinkled finish results which is of course undesirable. One of the particular advantages gained in the present invention is that this excessive reduction to carbon of the liquid component, such as mineral oil, is inhibited. We are not certain as to the reasons for this, but we believe that it may be related to the ethoxylated chains which the liquid phosphate esters possess, presumably taken together with the phosphate radicals.

We find also that with the compositions made up in accordance with the present invention we achieve a better peel when castings are broken out of the mold shortly after pouring.

We also find there is a great reduction in flaming on a quick shake-out subsequent to pouring. It is of course recognized that one ever present difliculty with nonaqueous molding compositions of the general type concerned here is that a certain amount of combustion takes place as a result of the ignition of the combustible portion by the hot metal. This can be hazardous, and in any case causes excessive consumption of the bonding ingredients. It is therefore a considerable advance to achieve the other advantages already set forth and at the same time reduce the flaming.

Some examples of proceeding in accordance with our invention will now be given:

Example 1 An alkyl ammonium humate was prepared by mixing together 10 parts by weight of North Dakota lignite, of the weathered, alkali-soluble variety described in US. Bur. Mines R.I., 5611, with 100 parts of water, suflicient borax to give an pH of 8.5, and then 3.6 parts of commercial di-methyl di(hydrogenated tallow) ammonium chloride. The resulting alkyl ammonium humate was recovered, dried and ground.

To four parts of this alkyl ammonium humate, which was di-methyl di(hydrogenated tallow) ammonium humate, 0.75 part of Liquid Phosphate Ester B was mixed with 0.25 part of diesel oil and 95 parts of silica sand. The particular sand used is known as Oklahoma No. 1 and has a grain fineness number of 85. This was mulled for 10 minutes and then tested and found to have a green compression strength of 9.4 lbs. per square inch. It was used to make a mold for a brass casting and the resulting casting was entirely satisfactory.

Example 2 An organophilic clay was prepared by mixing together milliequivalents of a commercial di-methyl di(hydrogenated tallow) ammonium chloride per 100 grams of commercial Wyoming bentonite with enough water to give a consistency appropriate for pugging the mixture, which was about 30 grams of water. A conventional pug mill was used. The resulting extrusions were dried and ground.

To two parts of this organophilic clay, which was dimethyl di(hydrogenated tallow) montmorillonite, one part of the same alkyl ammonium humate as described in Example 1 hereinabove, and one part of silica flour, approximately 200 mesh, was mixed with 0.75 part of the same liquid phosphate ester described in Example 1 hereinabove and 0.25 part of diesel oil, together with parts of silica sand, the same as used in Example 1. This was mulled for 10 minutes and found to have a green compression strength of 10.6 lbs. per square inch and a green shear strength of 4.1 lbs. per square inch. The composition was made into molds in which brass was cast, each casting weighing approximately 60 lbs. The castings were free of defects and had a good finish.

Example 3 In this example, the same alkyl ammonium humate and organophilic clay described in Examples 1 and 2 hereinabove were used. Two parts of the organophilic clay, 1.2 parts of the alkyl ammonium humate, and 0.8 part of 200 mesh silica flour were added to parts of a commercial silica sand known as Wedron C-10, the grain fineness number of which was /1 part of Liquid Phosphate Ester A and A part of light lubricating oil were mulled for 10 minutes, part of methyl alcohol being added at mulling, this additive being desirable but not essential. The sand was then tested by standard methods of the American Foundrymens Association and found to have a green compression strength of 7.1 p.s.i., a green shear strength of 2.7 p.s.i. and a hot compression strength at 1500" F. of 23 p.s.i.

Example 4 The procedure of Example 3 was carried out except that Liquid Phosphate Ester C was used. Again, excellent test values resulted, being 8.3, 2.7, and 33 for the green compression strength, the green shear strength, and the hot compression strength at 1500 F., respectively, all values being p.s.i. as before.

Example To 100 parts of the same sand described in Example 3 hereinabove there were added two parts of the organophilic clay and one part of the alkyl ammonium humate described in Examples 1 and 2 hereinabove. This was done in duplicate, and to one sample there was added a 3:1 by weight mixture of the liquid phosphate ester described in Example 1 hereinabove, and diesel oil. To the second duplicate batch, one part of straight diesel oil without the addition of any liquid phosphate ester was used. Both batches were mulled for 5 minutes and tested for green compression strength, green shear strength and hot compression strength at 1500 F. The values found were as follows:

The greatly superior results obtained by using the liquid phosphate ester in place of a portion of the diesel oil are readily apparent from the above test results.

Example 6 A molding sand composition was made up with the same sand, the same alkyl ammonium hurnate and the same organophilic clay described hereinabove in Example 3. The composition of the mixture was as follows: 100 parts of the sand; 3% parts of the organophilic clay; 1% parts of the alkyl ammonium humate; and /3 part each of Liquid Phosphate Ester B, of Liquid Phosphate Ester C and of diesel oil. No silica flour or other similar additive was used. Thus, in addition to the sand a total of 5 parts of solid additive and 2 parts of liquid additive were present. This mixture was mulled for 30 minutes and during mulling /2 part methyl alcohol was added. The finished molding sand composition exhibited good properties, hav ing a green compression strength of 14.0 p.s.i. and a green shear strength of 4.7 p.s.i.

Example 7 A molding sand composition was made up with the same sand as used in Example 1, the same alkyl ammonium humate as used in Example 2, and the same organophilic clay as used in Example 3. The composition of the mixture was as follows: 2000 grams sand, 30 grams Liquid Phosphate Ester B, 20 grams silica flour, 26.7 grams of the aforesaid alkyl ammonium humate, and 53.3 grams of the aforesaid organophilic clay. This molding sand composition was mulled for 10 minutes and then tested. It had quite satisfactory properties and showed a green compression strength of 6.0 p.s.i. and a green shear strength of 2.5 p.s.i.

As has been set forth, the long hydrocarbon chains of hydrogenated tallow are about 64% C that is, octadecyl, and approximately 30% of the closely related C or hexadecyl. In order to simplify the terminology here in, it will therefore be understood that when octadecyl is referred to, particularly in the claims which follow, this corresponds in a practical fashion to hydrogenated tallow hydrocarbon chains, since this is the most readily available commerical source of octadecyl radicals.

It will be seen that our invention accomplishes its objects. It should moreover be kept in mind that while we have explained our invention in terms of various specific materials, examples, conditions of manufacture, and the like, the invention is a broad one, and numerous variations of detail are possible and contemplated within the broad cope of the invention as defined by the claims which follow.

Having described our invention, we claim:

1. A molding sand composition, comprising sand, and a binder consisting essentially of alkyl ammonium humate, said alkyl having from 14 to 22 carbon atoms in a straight chain, together with from zero to four parts of organophilic clay chosen from the group which consists of organophilic montmorill-onite and organophilic attapulgite for each part of said alkyl ammonium humate, and an organic liquid consisting of from 25% to by weight of a liquid phosphate ester corresponding to the formula where R can be R or OH and R is:

R O(CH CH O where n varies from 2 to 18 and where R is chosen from the group consisting of straight chain alkyl radicals from C to C ortho R phenyl radicals and ortho-para di-R -phenyl radicals, said R being C8 to C12 alkyl,

the balance of 75% to 0% being a secondary organic liquid having a molecular weight of at least 125, said organic liquid being present in an amount within the range of to A; part for each part of said alkyl ammoniurn humate plus said organophilic clay, said molding sand having a green compressive strength of at least 2.4 lbs. per square inch.

2. The composition in accordance with claim 1 in which said alkyl ammonium humate is di-octadecyl dimethyl ammonium humate.

3. The composition in accordance with claim 1 in which said organophilic clay is di-octadecyl dimethyl arnmonium montmorillonite.

4. The composition in accordance with claim 1 in which said secondary organic liquid is a petroleum oil.

5. The composition in accordance with claim 1 which said said R is di-nonyl phenyl.

6. The composition in accordance with claim 1 which said R is di-nonyl phenyl, and said n is 10.

7. The composition in accordance with claim 1 which said R is di-nonyl phenyl, and said n is 15.

8. The composition in accordance with claim 1 in which said ammonium humate is di-octadccyl dimethyl ammonium humate, said organophilic clay is di-octadecyl dimethyl ammonium montmorillonite, said R is di-nonyl phenyl, said n is 15; and said secondary organic liquid is diesel oil, in proportions of approximately 75% of said liquid phosphate ester and 25% of said diesel oil.

References Cited by the Examiner UNITED STATES PATENTS 1,420,754 6/ 22 Rodman 260-515 1,861,685 6/32 Bussler 252-- XR 2,813,035 11/57 Sauter et a1 10638.2 XR

OTHER REFERENCES Chemistry and Industry, Humic Acid Investigation by Davies et al., November 23, 1957, page 1544.

ALEXANDER H. BRODMERKEL, Primary Examiner.

MORRIS LIEB MAN, Examiner. 

1. A MOLDING SAND COMPOSITION, COMPRISING SAND, AND A BINDER CONSISTING ESSENTIALLY OF ALKYL AMMONIUM HUMATE, SAID ALKYL HAVING FROM 14 TO 22 CARBON ATOMS IN A STRAIGHT CHAIN, TOGETHER WITH FROM ZERO TO FOUR PARTS OF ORGANOPHILIC CLAY CHOSEN FROM THE GROUP WHICH CONSISTS OF ORGANOPHILIC MONTMORILLONITE AND ORGANOPHILIC ATTAPULGITE FOR EACH PART OF SAID ALKYL AMMONIUM HUMATE, AND AN ORGANIC LIQUID CONSISTING OF FROM 25% TO 100% BY WEIGHT OF A LIQUID PHOSPHATE ESTER CORRESPONDING TO THE FORMULA 